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A
pple
bend apparatus and the specimen. For each
treatment, five replicate samples were bro-
ken with the chip bud proximal to the dis-
placement force (bud up), and five replicate
samples were broken with the chip bud distal
to the displacement force (bud down).
Each sample was categorized according to
the nature and location of the resulting break.
A clean break at the graft union was catego-
rized as a 1
st
order break. A break just above
the graft union but that included part of the
graft union was categorized as a 2
nd
order
break, as was a break just below the graft but
including part of the graft union. A break at
the graft union but with significant scion and
rootstock tissue remaining attached was cate-
gorized as a 3
rd
order break. Finally, trees that
broke well above or below the graft union, or
that did not break under maximum test dis-
placement were categorized as 4
th
order.
Data Analysis.
Means were calculated and
ranked for 2014 growth and break strength
data. The following variables were analyzed:
force (F), graft cross-sectional area (GCSA),
scion cross-sectional area (SCSA), F/GCSA,
and F/SCSA and height. Some of the trees
had the top few centimeters broken during
commercial harvest, so height measurements
in 2014 may not be accurate.
Fig. 1:
Apparatus used for 3-point flexural strength testing. Sample supported with 16 cm separation with flexural
strength and rigidity measured with a bench-testing machine. The sample shown is in "bud up" position where the
chip bud is situated proximal to the displacement force.